Geometry help

Selma is flying a kite. She lets out 80 feet of string. Her brother moves to a point where he is standing directly under the kite. He measures the distance to be 30 feet. How high is the kite? Please answer the question rounded to the nearest tenth.

Selma is flying a kite. She lets out 80 feet of string. Her brother moves to a point where he is standing directly under the kite. He measures the distance to be 30 feet. How high is the kite? Please answer the question rounded to the nearest tenth.